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Adaptive Leaf Size

Adaptive Leaf Size. Purpose:. What determines the size of leaves? Givnish and Vermeij (1976) suggested that leaf size is determined by the heat budget (the temp of the leaf) Test a model of optimal leaf size Givnish and Vermeij (1976) Tropical Forests. Key Concepts:. Convection:

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Adaptive Leaf Size

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  1. Adaptive Leaf Size

  2. Purpose: • What determines the size of leaves? • Givnish and Vermeij (1976) • suggested that leaf size is determined by the heat budget (the temp of the leaf) • Test a model of optimal leaf size • Givnish and Vermeij (1976) • Tropical Forests

  3. Key Concepts: • Convection: • The transfer of heat by the movement of a liquid or gas. (As opposed to radiation or conduction). L E A F A I R

  4. Key Concepts: cont’d • Boundary Layer • Layer of stagnant air • that naturally surrounds • an object LEAF (profile view) Air boundary layer

  5. Key Concepts: cont’d • Loss of heat to Leaf Convection depends on the boundary layer • Boundary layer thickness INCREASES with surface size. • Heat exchange DECREASES with boundary layer thickness. air air SMALL leaf (thin boundary layer) LARGE leaf (thick boundary layer)

  6. Key Concepts: cont’d • Evapotranspiration • Loss of water through stomata. • All leaves loose heat through evapotranspiration.

  7. Assumptions: •  Temperature :  Photosynthesis •  Temperature :  Water loss

  8. Wet Habitat: • water loss is not a problem • Maximizing photosynthesis is important • Sunny wet habitat: • Large leaf heats up past air temp • (max photosynthesis) • Shady wet habitat: • Small leaf equilibrates with air. A large leaf would become cool through evapotranspiration and retain that coolness because of its large boundary layer. • (max temp and max photosynthesis) Warm Leaves

  9. Dry Habitat: • Water loss = big problem • Water retention is important • Sunny dry habitat: • Small leaf equilibrates with air • (min temp and max water retention) • Shady dry habitat: • Large leaf remains cooler than air temp due to its larger boundary layer. Becomes cooler due to evapotranspiration. • (max water retention) Cool Leaves

  10. Identification:

  11. Methods: • Groups of 2 • Measure (L & W) • 30 leaves per • “treatment” • Centimeters • Start with third leaf back • Tuskegee Nat. Park • Smilax glauca • “Greenbriar vine” • 4 “Treatments”: • Dry & Sunny • Dry & Shady • Wet & Sunny • Wet & Shady L W

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